516 research outputs found

    Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

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    Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a ZZ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 <pT<100< p_{\textrm{T}} < 100 GeV and in the pseudorapidity range 2.5<η<42.5 < \eta < 4. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb1^{-1}. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

    Study of the BΛc+ΛˉcKB^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

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    The decay BΛc+ΛˉcKB^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} is studied in proton-proton collisions at a center-of-mass energy of s=13\sqrt{s}=13 TeV using data corresponding to an integrated luminosity of 5 fb1\mathrm{fb}^{-1} collected by the LHCb experiment. In the Λc+K\Lambda_{c}^+ K^{-} system, the Ξc(2930)0\Xi_{c}(2930)^{0} state observed at the BaBar and Belle experiments is resolved into two narrower states, Ξc(2923)0\Xi_{c}(2923)^{0} and Ξc(2939)0\Xi_{c}(2939)^{0}, whose masses and widths are measured to be m(Ξc(2923)0)=2924.5±0.4±1.1MeV,m(Ξc(2939)0)=2938.5±0.9±2.3MeV,Γ(Ξc(2923)0)=0004.8±0.9±1.5MeV,Γ(Ξc(2939)0)=0011.0±1.9±7.5MeV, m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV}, where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt Λc+K\Lambda_{c}^{+} K^{-} sample. Evidence of a new Ξc(2880)0\Xi_{c}(2880)^{0} state is found with a local significance of 3.8σ3.8\,\sigma, whose mass and width are measured to be 2881.8±3.1±8.5MeV2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV} and 12.4±5.3±5.8MeV12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}, respectively. In addition, evidence of a new decay mode Ξc(2790)0Λc+K\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-} is found with a significance of 3.7σ3.7\,\sigma. The relative branching fraction of BΛc+ΛˉcKB^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} with respect to the BD+DKB^{-} \to D^{+} D^{-} K^{-} decay is measured to be 2.36±0.11±0.22±0.252.36 \pm 0.11 \pm 0.22 \pm 0.25, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

    Measurement of the ratios of branching fractions R(D)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

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    The ratios of branching fractions R(D)B(BˉDτνˉτ)/B(BˉDμνˉμ)\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu}) and R(D0)B(BD0τνˉτ)/B(BD0μνˉμ)\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu}) are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb1{ }^{-1} of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τμντνˉμ\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}. The measured values are R(D)=0.281±0.018±0.024\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024 and R(D0)=0.441±0.060±0.066\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is ρ=0.43\rho=-0.43. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

    A new method to measure the time-integrated CPCP asymmetry in singly-Cabibbo suppressed D0D^0 \rightarrow K+KK^+K^- and DD0^{0} \rightarrowπ+π\pi^+\pi^- decays at LHCb.

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    A new method to measure time integrated C ⁣P{C\!P} asymmetry of D0D^0 singly Cabibbo-suppressed decays to the C ⁣P{C\!P}-even final states K+KK^+K^- and π+π\pi^+\pi^- is developed. The method is applied to decays produced in pppp collision and collected by the LHCb experiment between 2016 and 2018 at the center-of-mass energy of 13\,TeV and corresponding to an integrated luminosity of 5.7\,fb1^{-1}. The strong-interaction decay D+D0π+D^{*+}\rightarrow D^0\pi^+ is used to infer the flavour of the D0D^0 meson at production. The measured asymmetries are expressed as the difference between the raw asymmetries of the decays of interest and the raw asymmetry of the D0KS0π+πD^0\rightarrow K^0_S\pi^+\pi^- calibration channel. The final results are: ΔAC ⁣P(K+K)=AC ⁣P(K+K)AC ⁣P(KS0π+π)=0.194±0.049% \Delta A_{C\!P}(K^+K^-) = A_{C\!P}(K^+K^-)−A_{C\!P}(K^0_S\pi^+\pi^-)=0.194 \pm 0.049\% ΔAC ⁣P(π+π)=AC ⁣P(π+π)AC ⁣P(KS0π+π)=0.402±0.057% \Delta A_{C\!P}(\pi^+\pi^-) = A_{C\!P}(\pi^+\pi^-)−A_{C\!P}(K^0_S\pi^+\pi^-)=0.402 \pm 0.057\% where the uncertainties are statistical and the central values are blinded. The final uncertainty improves the world average statistical uncertainty, currently dominated by LHCb, by a factor of about 2.5

    A new method to measure the time-integrated CP asymmetry in singly-Cabibbo suppressed D0->K+K- and D0->pi+pi- decays at LHCb

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    A new method to measure time integrated CP asymmetry of D0 singly Cabibbo-suppressed decays to the CP-even final states K+K− and π+π− is developed. The method is applied to decays produced in pp collision and collected by the LHCb experiment between 2016 and 2018 at the center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5.7 fb-1. The strong-interaction decay D∗+ → D0π+ is used to infer the flavour of the D0 meson at production. The measured asymmetries are expressed as the difference between the raw asymmetries of the decays of interest and the raw asymmetry of the D0→Ks0π+π− calibration channel. The final results are: Δ ACP(K+K−) = ACP(K+K−)−ACP(Ks0π+π−)=0.194±0.049% Δ ACP(π+π−) = ACP(π+π−)−ACP(Ks0π+π−)=0.402±0.057% where the uncertainties are statistical and the central values are blinded. The final uncertainty improves the world average statistical uncertainty, currently dominated by LHCb, by a factor of about 2.5

    First measurement of the Zμ+μZ\rightarrow \mu^+ \mu^- angular coefficients in the forward region of pppp collisions at s=13\sqrt{s}=13 TeV